I've also found this cookbook recipe for updating instances after
reloading a module to be handy:
http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/160164
At the moment, I'm just going in via a manhole and manually reloading
modules when I change them in development. I'm sure this can be
automated, though.
This route has the advantage that you don't have to restructure your
code into non-objects in the way that the cookbook suggests.
Kevin